The aims of this thesis were threefold. First, medication related attitudes and behaviours were identified using in-depth qualitative interviews with parents of children with ADHD. Second, a questionnaire was developed to assess medication related attitudes and behaviours drawing from the data collected in the interview study. Third, the relationships between ADHD related attitudes and behaviours with family factors and cultural factors between the UK and the USA were examined. Parent and child version ADHD Medication Related Attitudes and Behaviours (AMRABs) questionnaires were developed to assess parents' and children's perceptions of the benefits, costs, stigma associated with ADHD medication and whether children resisted taking medication. Parents were also asked about the stigma they experience as parents, how flexible they are in administering medication and how competent they are in administering medication consistently. The questionnaires were piloted in ADHD clinics in the UK and USA, on the internet and through ADHD support groups. Participants in the UK consistently reported markedly higher levels of child stigma than participants in the USA. The final study examined relationships between the AMRABs subscales and family factors. The results indicated that child conduct problems were associated with resistance to taking medication. Maternal mental health difficulties were associated with maternal perception of the benefits and costs of taking medication, and with resistance to taking medication. Maternal ADHD and poor parenting self-efficacy were associated with difficulties in administering medication consistently. Family cohesion was predictive of child stigma in the USA, and paternal warmth and high maternal criticism were associated with child stigma in both countries. However, the most significant predictor of child stigma was being from the UK. High SES was associated with higher parental stigma.